Abstract
Doping plays a vital role in the application of transition-metal dichalcogenides (TMDCs) because it can increase the functionality of TMDCs by tuning their native characteristics. In this study, the influence of Mn, Fe, Co, and Cu doping on the photoelectric properties of HfS2 was investigated. Pristine, Mn-, Fe-, Co-, and Cu-doped HfS2 crystals were grown using the chemical vapor transport method. Scanning electron microscopy images showed that the crystals were layered and transmission electron microscopy, X-ray diffraction, and Raman spectroscopy measurements confirmed that the crystals were in the 1T-phase with a CdI2-like structure. The bandgap of pristine HfS2 obtained from the absorption and photoconductivity spectra was approximately 1.99 eV. As the dopant changed from Mn, Fe, and Co, to Cu, the bandgap gradually increased. The activation energies of the samples were determined using temperature-dependent current-voltage curves. After doping, the activation energy decreased, and the Co-doped HfS2 exhibited the smallest activation energy. Time-resolved photoresponse measurements showed that doping improved the response of HfS2 to light; the Co-doped HfS2 exhibited the best response. The photoresponsivity of HfS2 as a function of the laser power and bias voltage was measured. After doping, the photoresponsivity increased markedly; the Co-doped HfS2 exhibited the highest photoresponsivity. All the experimental results indicated that doping with Mn, Fe, Co, and Cu significantly improved the photoresponsive performance of HfS2, of which Co-doped HfS2 had the best performance.
Highlights
Transition metal dichalcogenides (TMDCs) [1,2,3,4,5,6,7,8,9] refer to the compounds of transition metal (TM) elements from group IVB to group VIIB in the periodic table and chalcogen elements
SEM images showed that the HfS2 crystals were layered materials, with an angle of 120◦ characterizing the edge of each layer
The TEM and XRD results showed that the HfS2 crystals had a
Summary
Transition metal dichalcogenides (TMDCs) [1,2,3,4,5,6,7,8,9] refer to the compounds of transition metal (TM) elements from group IVB to group VIIB in the periodic table and chalcogen elements. They have the general chemical formula TX2 , where T represents a TM atom, and X represents a chalcogen atom such as S, Se, or Te. TMDCs are layered materials in which one unit layer is composed of three atomic planes. Graphene-like two-dimensional (2D) freestanding monolayers [11] Such 2D TMDCs with atomic-scale thicknesses exhibit a direct bandgap and strong spin-orbit coupling
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